Rotating radio beacon



May 13, 1952 F. DE. FREMERY ROTATING RADIO BEACON Filed Feb. 1l. 1947 FRANK o: frm-:MERY .sx/,-

HGENT Patented May 13,Y 1952 l u 2,596,5:r1f4 t 5" nors'rmaasnlo BEACON Frank `de 4iFremiery, n Eindhoven, Netherlands, as signor tov Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application February 11, 1947, Serial No. 7727,7.66

` In the Netherlands February 5, 1944 section 1, Public Law 69o, August s, 194s i Y Patentexpires February 5, 1964 The copending patent application, Serial Number 680,901,7led July 2, 1946, now U. S. Patent No. aeaoodissued November 21, 195o, describes a method of determining the direction in which a receiver is located with respect to albe'acon transmitter by means of the angle', enclosed by the direction `to be determined and a known di-i rection of orientation, which method consists in that a measuring characteristic, which is a measure of the angle is derived from the mutual location of two oscillations which have different frequencies w and no and which are in harmonic relation to each other,vsaid oscillations being pro` duced in such a manner that the oscillation` of the lower frequency has a phasecorresponding to the angle and the other oscillation has a phase independent of the angle If n is greater than one, this method permits of determining the angle with very great accu# racy, since a measuring characteristic,`which is a function of n, may be derived from the mutual location of the two oscillations w and uw. u

In fact, 'ifthe two oscillations a and no are so transmitted that in the direction of orientation the two oscillations o and nw pass at least once simultaneously through zero in each periodof the oscillation of the lower frequency, two oscillations are obtained in an arbitraryFdirection enclosing an angle with the direction of orientation, of which one is proportional to sin (ot-i5) and the other proportional to 'sin not. The angle ,8 to be determined may be derived from the two oscillations in different mannersLfor example by that the oscillation of the lower frequency obtained after detection is multiplied n times '1n frequency, resulting in an oscillation which is proportional to sin nwti-n). By determining the phase angle which exists between the oscillation multiplied in frequency and the oscillation of the higher frequency obtained after detection, which is proportional to sin not, there is obtained a measuring characteristic which is determined by n, so that a higher accuracy in measurement is attained.

However, in the space surrounding the beacon device there are formed nsectors in whichthe measured angle no varies each time of from 0 to 21r radials, so that the measuring characteristic obtained indicates only the possible location of the direction to be determined in one of these sectors, the spatial angle thus notV being determined unambiguously by the measured value in question.

According to the invention, in order that in those cases in which the ambiguity of the meass claims.lv (creia-Line) uring characteristic may lead to disturbances, this ambiguity may be eliminated, a third oscillation having a frequency which is in harmonic relation with at least one of the oscillations u and no is transmitted in such a manner that the mutual location of the third oscillation and of the oscillation having the frequency w or no, which is in harmonic relationthereto, may have derived from it a measuring characteristic which is an unambiguous measure of the angle Preferably, Ythe frequency of the third oscillation will be half, or twice, or a higher harmonic ofthe oscillation having the lower or the higher Y, frequency, the phase of the third oscillation varying with direction in the same sense as that of the'oscillation having the frequency w or no. Y.

"Another example of the method` according to the inventionV consists in that the' frequency .of the third oscillation is'an underharmonic of the oscillation having the lower frequency (in-,fthe

`phase of the third oscillation being independent by these two indications, which indicate respectively the exact locationof the direction to be determined in a definite sector and the spatial sector concerned. Y

A particular advantage of the method according to' the invention consists in that the 'object aimed at can be attained with a minimum of additional means in the beacon transmitter and the receiver. This more particularly applies t0 those cases wherein the third oscillation is transmitted modulated on a carrier wave of the same frequency as the oscillations w and no, as is preferably the case.

'I'he mutual location of the third oscillation and the two other oscillations is preferably such that these oscillations pass at least once simultaneously through zero in each period of the oscillation having the frequency w. By this adjustment it is ensured that the two indications and n have a common direction of orientation. A

In order that the invention may be clearly understood and readily carried into eflect,V it will'now be described more fully with reference to the accompanying drawing.

In the drawing:

Fig. 1 is a block diagram of a beacon transmitter in accordance Ywith the invention,

Fig. Z is a block diagram of a beacon receiver in accordance with the invention, and

Fig. 3 is a modification of Fig. 2.

Figurey 1. shows diagrammatically. a.. form of construction of al' beacon device adaptedforuse of the method according to the invention. In this beacon device high-frequency oscillations are produced by an oscillator I, which are supplied;- if desired through a frequency-multiplier"Zf'andf4 a high-frequency amplifier 3, to a modulator and two push-pull modulators E'andfS in Wliichl push-pull modulators the high-frequencyjoscillaetions are modulated with suppression lof the carrier wave by two oscillations'havingfrequeni-l cies w and Zw which are in harmonic relation. to each other. The modulating oscillationhaving` the frequency w is produced by means of"anoscil'f:^y lator 'I' and is supplied, on the one hand, to thel modulator 5 via an amplifier 8 and, onlthe--otlier theoscillatorl by means of a frequency-multig plierlaand' supplied, via an amplifier I4, to the modulatorflifand in this modulator, modulated on the`fhi'gh'frequ'ency oscillations supplied to it.

Furthermore; therbeacon device shown in Figa uref 1," comprises: four vertical dipole-aerials I5, I6;` I .'I and. I8 which are placed'in' the corner points of "a square and' which arenormalto the planefofdrawing; an aerial I9 being;arranged inlthecentreof thesquare and in parallel to the other aerials.

Theioscillations produced in theoutput circuit vof tha-modulator# aresuppliedrto the central aerial II 9*,.whereas the oscillations producedin the outputcircuits of the modulators 5 and 6 are supplied in anti-phase to the aerials- I5, I1 and I.6;'I Iii-respectively;located :inthediagonal points ofthesquare.

Consequently, in thedevice described the aerialspla'ced in the corner'pointsofthe-square are so fed that the phase displacements between the: modulation'V of the modulatedA oscillations supplied to;v each pairV of adjacent iaerials-is equal to thezspatial angleA of 90 'which exists-between the tWo aerials. Thus, a'v high-frequencyv eld modulated'by the oscillations w and Zw is so radiatedthat the phase of Veach of the oscillations obtained after.- detection is dependenton direction.

The phase-displacing device-s 9 andfIZ are so adjustedthat thevcurrentin the aerial Iisleadingr' and' lagging respectively for the twooscillationswand -Zw with'respect to that Ain the other aerials, dueto which'the phases of the-modujlations w and Zw vary with directions in the'same Sense;

The high-frequency field modulated by the oscillation having thefrequency nw and radiated byfthePaerial I5V is such that the phase of the .oscillationobtained after detection is independent of direction.

By means of phase-displacing device 2d it can be ensured that the mutual location of the three oscillations, w, uw and Zw obtained after detection is fixed in a definite direction (direction of orientation) and is preferably such that the three oscillations pass at least once simultaneously throughzero in each period of the oscillation having-l the lower frequency.v In ant arbitrary direction enclosing an angle 'with the direction of orientation three oscillations are thus obtained after detection, of which one is proportional to vsin (wt-kL-the second proportional to sin nwt and the third proportional to sin (Zwt-).

According to' thef invention, the angle to be determined may-'be` derived from the oscillations sin (wt-) and sin nwt as well as from the oscillationssin (wt-) .and sin (Zwt-) Asdescribedtin the above-identified copending application, vthe angle to be determined may be derived from the oscillations sin (wt-) and sin'nwt by'that the oscillation of the lower frequency' obtained after detection is multiplied n times in frequency, resulting in an oscillation which is proportional to sin (rmt-nm... B ydetermining thephase angle which existsbetween the oscillation multiplied in frequency and the oscillation of the higherY frequencyV obtained after detection, which. is proportional tosinnwt, there is obtained a measuring characteristic which is determined by n.

Similarly, oscillations proportionalV to (wt-) and sin (.Zwt-) may have'derived'from a-measuring characteristic. which is determined by (1p-1) since in this case 11:2. y.

Consequently, by means of asmall extension of thetransmitting equipment,.i.V e.. by the ar.- rangement of the devices I I and I2, the ambiguity of the exact indication obtained. by the transmission of the oscillationsw` and :'rwis complete.-v

ly obviated which appreciably increases.,f thefuse-l fullness ofthe method described. in the main-.ap-

plication.. y p

A. constructional Yexample ofthe device: adapt-- ed to. ther receptionv of. thev oscillations emitted by the device of Figurel .is shown inFigure. Z.. In this device the modulated. oscillationsfreceived' in an aerial ZO- are supplied to r a high-.frequency amplifiertZ-I, which is connected 1in-.cascade;.to..a mixing-stage 22, an intermediate-frequency. amplifier 23, and a detector 24. The outputlcircuit ofthe detector includes three filters.` 25, 26,and 2:1, which are tuned respectivelyto the.v frequencies w. nw and Zw, Y l

To derive theangle from. theoscillation'sfw andnw, the oscillation of the-lowerlfrequencyfis supplied via4 a frequencyv multiplier 28 andeJ switch 29 and the oscillation. havinga. frequency nw is supplied'via aswitch tosa phase-meter 3l, which determinesthe phase angle n .which exists-between the'oscillationof the lower frequency multiplied n times in frequency, and the oscillations of the same frequency nw. In the other position. ofV thev switches 29rand. 39..theos cillation having thefrequency w vis suppliedvia a frequencyV doubler. 32 Vand the. oscillationy having the frequency- Zw is supplied. directly to thephase meter 3|. In this position the phase anglewhich exists' between the oscillations supplied to the phase meter is equal to by which the ldirection to ybe determined is fixed unambiguously."

It is evident thatv for deriving aV measuring characteristicwhich is proportional to n. and respectivelyl from the mutual location.l of 'the oscillations of the frequencies w and nw, and w and. Zwy respectively, obtained inthe receiver after detection, use may alternatively be made of a device different from that shown in Figure 2.- For example, as shown in Fig. 3, use'may be sin made of a cathode-ray tube 33 having two deilecting devices arranged at right angles to each other, which have supplied to them the oscillations w and no and w and 2o respectively which occur in the output circuit of the detector 24.

The receiving device described can be used not only for the reception of oscillations emitted by the device of Figure 1, but is on principle adapted to the reception of any beacon devices which are applicable in the method according to the invention. In this case it is only necessary for the filters included in the output circuit of the detector 24 to be tuned respectively to the three oscillations emitted by the beacon transmitter.

In a receiving device according to the invention use is preferably made of an automatic volume control or of a limiter, in order to obtain an indication independent of the amplitude of the oscillations w, no and 2u.

What I claim is:

1. In a radio beacon, a transmitter comprising means for propagating in space a suppressed carrier wave with a iirst modulation component having a space-phase depending on bearing, means for propagating in space a carrier Wave with a second modulation component having a space-phase independent of bearing, the frequency of said second modulation component being a harmonic of the first modulation component, and means further imposing on said suppressed carrier wave a third modulation component having a space-phase depending on bearing, the frequencies of said rst and third components being harmonically related.

2. A transmitter, as deiined in claim 1, wherein the frequency of said third component is one half the frequency of said first component.

3. A transmitter, as defined in claim 1, wherein the frequency of said third component is twice the frequency of said first component.

4. In a radio beacon, a transmitter comprising a carrier wave source, first, second and third oscillatory modulation sources, the frequency of the second modulation being a multiple greater than two of the frequency of the first modulation, the frequency of the third modulation being twice the frequency of the first modulation, a pair of balanced modulators, means to apply said first and third modulations in phase quadrature as an input to said balanced modulators, means to apply said carrier wave as an input to said balanced modulators to combine with the modulations therein, said1 carrier wave being suppressed in said balanced modulators, an amplitude modulator, means to apply said carrier wave and said second modulation as an input to said amplitude modulator, first antenna means coupled to the output of said amplitude modulator for radiating said carrier wave with said second modulation omnidirectionally, and second antenna means coupled to the output of said balanced modulators and disposed in predetermined relation to said rst antenna means for radiating a rotating eld constituted by said suppressed carrier wave with said first and third modulations, the space-phase of said modulations being a function of bearing.

5. An arrangement, as set forth in claim 4, wherein said second antenna means includes four radiating elementspositioned at the corners of a square, one of the balanced modulators being coupled to one pair of diagonally opposed elements for energizing said elements in opposite phase. the other of the balanced modulators being coupled to the other pair of diagonally opposed elements for energizing said elements in opposite phase.

6. In a radio beacon system, a transmitter comprising a carrier wave source, an oscillatory modulation source, a pair of balanced modulators, an amplitude modulator, means to apply said carrier wave as an input both to said amplitude modulator and said balanced modulators, means to apply the original modulation of said modulation source in phase quadrature as an input to said balanced modulators, a frequency doubler coupled to said modulation source, means to apply the doubled modulation from said doubler in phase quadrature to said balanced modulators, said balanced modulators .being arranged to suppress said carrier wave, a frequency multiplier coupled to said modulation source, means to apply said multiplied modulation as an input to said amplitude modulator, first antenna means coupled to the output of said amplitude modulator for radiating said carrier wave with said multiplied modulation omnidirectionally, and second antenna means coupled to said balanced modulators and disposed in predetermined relation to said first antenna means for radiating a rotating neld constituted by the suppressed carrier wave with said original modulation and said doubled modulation.

7. A transmitter, as defined in claim 6, further including an adjustable phase shifter interposed between said modulation source and said balanced modulators for effecting a predetermined phase relation between said original modulation and said doubled and multiplied modulations.

8. In a radio beacon system wherein a carrier wave With rst and third modulation components is radiation and a carrier wave with a second modulation component is radiated, the frequency of said third component being double the frequency of said first component, the frequency of said second component being a multiple greater than two of said rst component, said rst and third components having a spacephase depending on bearing and said second component having a space-phase independent of bearing, a receiver for said waves comprising means to detect and demodulate said waves to derive said components therefrom, filter means coupled to said demodulation means to separate said demodulated components, means to double the frequency of the separated iirst component, means to multiply the separated first component and phase indicating means to compare said multiplied rst component with said second component and to compare said doubled first component with said third component to determine the bearing.

FRANK DE FREMERY.

REFERENCES CITED The following references are of record in the l'ile of this patent:

UNITED STATES PATENTS Number Name Date 1,922,677 Greig et al. Aug. 15I 1933 2,252,699 Byrne Aug. 19, 1941 2,253,958 Luck Aug. 26, 1941 2,394,157 Earp Feb. 5, 1946 2,422,110 Luck June 10, 1947 FOREIGN PATENTS Number Country Date 385,521 Great Britain Dec. 29, 1932 

